PMC

Photograph of the placental vascular surface. The black arrow indicates the anastomoses between the acardiac fetus and the direct pump fetus. The white arrow indicates the anastomoses between the direct pump fetus and the indirect pump fetus. ① is the anastomoses between the umbilical artery of the direct pump fetus and the umbilical artery of the indirect pump fetus. ② is the anastomoses between the umbilical vein of the direct pump fetus and the two umbilical veins of the indirect pump fetus. The gray arrow indicates the direction of blood flow in the vascular anastomoses.

(a1): Hematoxylin and eosin (HE) staining of the skin of the Fetus acardius amorphus. Fetus acardius amorphus shows differentiated skin tissue, with a stratum corneum, an epidermis, a dermis and a subcutis. Images are shown in 4x magnification. (a2 and a3) Hematoxylin and Eosin (HE) staining of the core mass of the Fetus acardius amorphus. Fetus acardius amorphus shows organized bronchus-like structures with respiratory epithelium, goblet cells and cilia (black arrow) on the surface. Images are shown in 4x magnification (a2) and in 40x magnification (a3). (b1 and b2) Hematoxylin and Eosin (HE) staining of the core mass of the Fetus acardius amorphus. Fetus acardius amorphus shows differentiated bone and cartilage with bone marrow cells like megakaryocytes, erythrocyte precursor cells as well as myelocytes in between. Images are shown in 10x magnification (b1) and in 40x magnification (b2). (b3 and b4) Hematoxylin and Eosin (HE) staining of the core mass of the Fetus acardius amorphus. Fetus acardius amorphus shows differentiated skeletal muscle with long, shapoid myocytes with an ovoid nucleus in the center. Images are shown in 10x magnification (b3) and in 40x magnification (b4). (c1 and c2) Hematoxylin and Eosin (HE) staining of the cyst-like structure in the Fetus acardius amorphus. Fetus acardius amorphus shows differentiated neurons of the hippocampus. Images are shown in 10x magnification (c1) and in 40x magnification (c2). (c3 and c4) Hematoxylin and Eosin (HE) staining of the gonadal glands in the Fetus acardius amorphus. Fetus acardius amorphus shows gonadal glands with well-formed seminiferous tubules showing Ledyig cells between (black star), and spermatogonia (black arrow) and Sertoli cells (white star) inside. Images are shown in 10x magnification (c3) and in 40x magnification (c4).

Proposed evolutionary relationships of C. fetus subspecies. 16S rRNA analysis, MLST data, and DNA hybridizations suggest that C. fetus subsp. originate from an ancestral reptile strain. C. fetus subsp. fetus serotypes A and B correspond to the two different surface array protein (sap) types A and B expressed in strains adapted to mammals. C. fetus subsp. venerealis (exclusively type A) is considered a bovine clone evolved from subsp. fetus. Reptile C. fetus subsp. fetus are type A and are genetically more diverse than mammalian C. fetus subsp. fetus types A and B. It is proposed, therefore, that they represent a distinct, still unclassified subspecies (adapted from Ref. []). The frequency at which the respective subspecies cause human infection is indicated with plus marks (+ to +++).

Agarose gel electrophoresis of PCR products obtained by using primer pairs MG3F-MG4R (lanes 1 to 7) and VenSF-VenSR (lanes 9 to 15). Lanes: 1 and 9, C. fetus subsp. venerealis 69/05; 2 and 10, C. fetus subsp. venerealis 70/05; 3 and 11, C. fetus subsp. fetus 91/05; 4 and 12, C. fetus subsp. venerealis 122/05; 5 and 13, negative control; 6 and 14, C. fetus subsp. fetus type strain; 7 and 15, C. fetus subsp. venerealis type strain; 8, size marker.